The Effect of Biosurfactant Isolated from Actinobacteria on the

introductionAeromonas hydrophila, a rod-shaped, gram-negative bacterium, is frequently found in aquatic surroundings and additionally present in drinking water, sewage, and food sources. This microbe is gaining recognition as a potential threat to health, classifying it as an emerging pathogen. Biosurfactants are microbial-derived compounds that share hydrophilic and hydrophobic moieties that are surface active. This study aimed to investigate the effect of biosurfactant isolated from Actinobacteria on the expression of the bfp gene of A. hydrophila isolated from children's stool samples to patent the ideal method in Qom, Iran, from May 2022 to March 2023. MATERIALS AND

methodsActinobacteria were isolated from soil samples of the desert areas of Qom province, Iran. Biochemical and molecular tests of 16S rRNA were used to identify Actinobacteria isolates. The produced biosurfactant was investigated by methods of hemolysis, oil droplet destruction, lipase production, oil expansion, emulsifying activity, and surface tension reduction measurement. The structure of biosurfactant was investigated by Fourier transform infrared spectroscopy (FTIR) analysis, and its effect on bfp gene expression was measured. Also, isolates of A. hydrophila were obtained from stool samples of children referred to Hazrat Masoumeh Hospital in Qom from May 2022 to March 2023. Then, the effect of a biosurfactant isolated from Actinobacteria on the bfp gene expression of A. hydrophila isolates was measured by RT-PCR.

resultsBased on sequencing data, the Streptomyces genus with the ability to produce biosurfactant was isolated from the soil of the studied area, which could reduce the expression of the bfp gene after treatment with biosurfactant in clinical isolates of A. hydrophila. DISCUSSION: The biosurfactant-producing isolates were identified as Streptomyces spp. The results indicated that the biosurfactant significantly decreased bfp gene expression in A. hydrophila. This emphasizes the potential of biosurfactants to eliminate microorganisms by reducing virulence gene expression, inhibiting biofilm formation, demonstrating antimicrobial activity, and improving emulsification. The study supports the idea that biosurfactants can interfere with bacterial mechanisms that cause disease, such as biofilm formation, which is critical for pathogen persistence and resistance. Previous research also confirms the antipathogenic activity of natural isolates against A. hydrophila.

conclusionThe findings of the present study show that the desert soils of Qom province are a potential area for finding actinobacterial isolates with the ability to produce biosurfactants and influence the expression of pathogenic genes of clinical isolates of A. hydrophila.